US2161218A - Rural line repeater - Google Patents

Description

RURAL LINE REPEATER Filed March 16, 1958 ooN INVENToRs. CARL o. WRIGHT BY EDWARD s. PETERSON Patented Junee, 1939 UNITED STATES PATENT ori-ics RURAL LINE REPEATER Carl Oman Wright, Chicago, and Edward Sigford Peterson, Elmwood Park, Ill., assignors to Associated Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Application March 16, 1938, Serial No. 196,114

1,9 Claims.

up connections between the various lines ofthe system.

In the usual arrangement of existing installed automatic exchanges wherein certain of the lines extending to the exchange are of the rural multiparty type and othersare of the single party type, no difierentiationis made between the lines as regards the mode of terminating the lines in the automatic switching equipment. As a result, the

initiation of revertingr calls on the rural lines invariably results in the seizure of certain of the automatic switching equipment provided in the terminating exchange. More particularly, when a reverting call is initiated on a rural line, one

of the non-numerical automatic switches provided in the exchange is assigned to the use of the line having the calling condition created thereon and operates to switch the calling line through to one of the numerical switches. In certain instances the seized switches are held operated throughout the duration of the reverting call. In other systems, apparatus is provided for causing the release of the operated switches after a predetermined time interval has elapsed following the seizure of the switches. In either case, certain of the automatic switching equipment is tied up so that it cannot be used by the other lines.

It is aV further object of the present invention,

55 therefore, to provide in an automatic telephone system improved apparatus of exceedingly simple arrangement for preventing any of the regular switching equipment from being taken for use by a line having access to the equipment when a reverting call is initiated on the line.

It is a further object of the invention to provide improved apparatus of extreme simplicity for guarding the rural lines against seizure by the automatic equipment when the lines are engaged with calls of the reverting type.

In the illustrated embodiment of the invention, the several multiparty rural lines of the system extend to an automatic exchange and are arranged to have access to certain of the non-numerical automatic switches provided in the exchange and to be accessible to certain of the numerical switches also provided in the exchange. More particularly; each rural line terminates in a' repeater, and each repeater is connected by Way of a trunk line to the automatic switching (Cl. 179-17) v equipment. ,Each rural line has associated therewith a plurality of local battery substations and each of the substations conventionally comprises a telephone, an impulsing device, a hook switch for connecting the telephone across the conductors of the associated line, and an alternating current magneto generator adapted for use in signaling between the substations of the associated line on reverting calls. In accordance with one feature of the present invention there is provided in each repeater a relay operative in response tothe operation of any one of the generators provided in association with the associated line for preventing the line from taking any one of the non-numerical switches for use and ,l5

for marking the associated line as busy, thereby to prevent the line from being seized by any one of the non-numerical switches. Also included in each repeater is a pulsing relay which is operative to complete a loopcircuit to one of the nonnumerical switches when a regular call is initiated on the associated line and is arranged to respond to impulses dialed at the calling substation and to repeat the impulses to the automatic switching equipment. For the purpose of marking the respective rural lines as busy, when reverting calls are initiated at the substations associated therewith, there is provided a timing device which is operative through a predetermined cycle each time its operation is initiated and is arranged to hold operated for a predetermined time interval any operated ones of the relays respectively associated with the rural lines which function individually to mark the respective lines as busy. This timing device comprises a switch having a home position and operative to a predetermined off-normal position, an output terminal, a start relay, apparatus responsive to the operation of the start relay for initiating the operation of the Switch, and apparatus controlled by the start relay and the switch for applying and maintaining a predetermined potential on the output terminal for a predetermined time interval. The start relay is connected and arranged to respond to the operation of any one of a plurality of alternating current relays individually associated with the respective rural lines and the arrangement is such that the switch incorporated in the timing device is returned to its home position to start a new cycle of operation of the timing device each time one of the alternating current relays is caused to operate.

A further feature of the invention relates to the provision of a test connector switch by way of which a connection may berouted to any of the rural subscribers lines for the purpose of determining the condition of these lines. Each of the lines is normally connected to be accessible to the regular connector switches, but there is provided in association with each line a line switching relay arranged to be controlled by the test connector switch and operative to rearrange the circuit connections so that the associated line is accessibile to the test connector switch. In order to prevent this test connector switch from seizing the lines at times when they are busy, certain of the control relays embodied in the respective repeaters and operative when the associated lines are made busy in connections not routed by way of the test connector switch, are arranged to render the test connector switch ineffective to control the particular line switching relay associated therewith.

Further features of the invention pertain to the particular arrangement of the circuit elements whereby the above-outlined operating features are obtained.

The novel features believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the specification taken in connection with the accompanying drawing. In the drawing, Figures 1 and 2 illustrate an automatic telephone system having incorporated therein the features of the present invention as briefly outlined above.

Referring now to the drawing, the system there illustrated comprises, in general, an exchange, a plurality cf single party subscribers lines, two of which are indicated at |l2 and |'i3 extending to the exchange, and a plurality of subscribercontrolled automatic switches including the two line switches IB and 50, respectively, a selector switch 20, and two connector switches 3@ and 4U respectively, for setting up connections between `the various subscribers lines. It is pointed out that the line switches l0 and 50 and the other similar switches corresponding thereto are nonnumerical switches in the sense that they are ineifective to perform any line selecting functions other than those of selecting idle ones of the selector switches. The selector and connector switches, on the other hand, are commonly known as numerical switches in that they are operative to perform particular line selecting functions in response to impulses transmitted thereto. It will be understood that a plurality of switches of each type, namely, a plurality of line switches, a plurality of selector switches, and a plurality of connector switches, are provided in the system for performing the usual line switching functions, The switches of each type are respectively arranged in groups and, in accordance with universally followed practice, the number of switches in each group is determined by the maximum Volume of traffic the particular switch group is required to handle. Further in accordance with conventional practice, each of the automatic subscribers lines is multipled between the corresponding bank contacts of a group of connector switches, whereby a plurality of such switches are available for setting up connections between each line and every other line of the system. The line switches, on the other hand, are individually associated with the respective subscribers lines, that terminating the line |12 being indicated at I0.

Aare several commercial embodiments.

The end of each automatic subscribers line remote from the exchange terminates in a subscribers substation which may be of any desired arrangement. Two such substations are diagrammatically illustrated at B and Cin association with the lines H2 and H3, respectively. In brief, each of the substations may comprise the usual hand set type of transmitter and receiver, a hook switch, a ringer, and an impulsing device for transmitting the switch control impulses by way of the associated line to the automatic` switching equipment located in the terminating exchange.

Each of the line switches IIJ, 5B, etc., is preferably of the well-known rotary type, of which there Each of the selector and connector switches is preferably of the well-known Strowger type having embodied therein a wiper carriage structure adapted to be translated vertically to bring the wipers thereof to a position opposite a particular level of bank contacts and then rotated to bring the wipers into engagement with a particular set of contacts in a selected level; vertical, rotary and release magnets; and control relays suitably connected and arranged to control the energization of the various magnets and the line switching in accordance with the particular functions of the switch. Obviously, the particular arrangement of the control apparatus embodied in the switches of different type is diierent in each instance dcpending upon the character of the switch.

Also extending to the exchange housing the automatic switching equipment briefly described above are a group of rural subscribers lines, one of which is indicated at 85. Each of these lines is of the multiparty type having associated therewith a plurality of subscribers substations. One such substation is illustrated in detail and indicated generally at A in association with the line 36, and a second substation associated with the same line is indicated diagrammatically at D. Each of these rural lines terminates in a repeater, and each repeater is connected by way of a trunk line to have access to and to be accessible to the automatic switching equipment provided in the exchange Thus, the line 86 terminates at a repeater l which is connected by way of a twoway trunk line |55 to the non-numerical line switch 50 and the numerical connector switch 55. For the purpose of marking the various rural lines as busy when these lines are respectively engaged in reverting call connections, there is provided a timing device indicated generally at 2m! which is commonly associated with all of the rural subscribers lines. This device cooperates with certain of the control relays provided in the respective repeaters to busy the repeater trunk lines when the respective associated subscribers lines are occupied with reverting calls.

Code ringing is utilized for selectively signaling the various substations associated with each of the rural subscribers lines. To this end, suitable provisions are made in the connector switch ii and the other corresponding switches for selecting the proper coded ringing current to signal a desired substation on a selected line.

Neglecting for the present the details of the apparatus provided in association with the rural subscribers lines, the system as described above is, in general, entirely conventional in form and its operation is well understood in the art. In brief, when a subscriber, such, for example, as the subscriber at the telephone B, initiates a call over the line |12 to a second subscribers telephone, such, for example, as the telephone C, by lifting his receiver from its hook, a loop circuit is completed for initiating the operation of the line switch I0 to select a trunk line leading to an idle selector switch. Assuming, for example, that the selector switch 20 is the first numerical switch selected by the line switch I for the use of the calling line |12, when the trunk line leadink to this selector switch is found, the loop circuit is extended to this selector switch and the switch is conditioned to respond to the rst series of impulses dialed at the calling substation. With the selector switch 20 in this condition, dial tone is returned over the established loop to the calling subscriber to indicate that the dialing operation may be started. When the first digit is dialed at the calling substation, the switch 20 elevates its wipers to a position opposite the level of bank contacts terminating the trunks leading to the connector switches having access to the called line |13. Following this operation, the wipers of the switch 20 are automatically stepped over the contacts of the selected level until a trunk leading to an idle connector switch of the selected group is found. Assuming that the connector switch 3D is the first idle connector switch available in the selectedv group, when the wipers of the switch 20 are stepped into engagement with the contacts terminating the trunk extending to this connector switch, the subscribers loop circuit is extended thereto, thereby to cause this connector switch to be conditioned to respond to the second and third series of impulses dialed at the calling substation. In response to the dialing of the second digit, the wipers of the connector switch 3'0 are stepped vertically to a position opposite the level of bankcontacts at which are terminated the lines of the ten-line group including the called line |13. Following this series of impulses, the connector switch is conditioned to rotate its wipers step by step in accordance with the impulses making up the third and final digit dialed at the calling substation. W'hen the last digit is dialed, the wipers of the switch 30 are stepped into engagement 'with the set of bank contacts terminating the called line |13. In accordance with conventional practice, suitable provisions are made for testing the called line to determine its idle or busy condition, for returning busy tone over the established loop to the calling subscriber in case the called line is busy, an-d for applying ringing current to the called line in the event this line is idle at the time it is selected. Assuming that the called line is idle, the desired conversational connection is completed when `the called substation is answered. Also in accordance with conventional practice, the apparatus is arranged to insure its release when the connection is cleared out at the calling and called substations. Any desired mode of initiating the release of the established switch train may be utilized. For example, the control apparatus embodied in the connector switch 3i) may be arranged sothat the release of the connection is entirely under the control of the calling part. Alternatively, the apparatus may be so arranged that the release Vof the connection is under the control of the last party to hang up.

Referring now more particularly to the apparatus provided in association Awith the several rural lines, it is pointed out that the arrangement of the substation equipment may be identical for all of the substations. For this reason, only the apparatus located at the substation A- has'been illustrated in detail. In brief, this lapparatus comprises a transmitter 13, a receiver 14, and means comprising a hook switch 80 for connecting the Vtwo elements noted to the associated Yline. This substation is of the local battery type, a battery being provided as a vehicle for generating voice frequency voltages when sound waves impinge upon the diaphragm of the transmitter 13. Such voltages are impressed between the conductors C81 and C88 of the line 86 by a transformer 1I). There is also provided at the substation A a signal device 16 in the form of a polarized ringer, a manually operable alternating current generator 18, and a dialA actuated impulsing device 11.

The repeater |63 at which the line B6 terminates is identical in all respects with the other repeaters respectively associated with the other rural subscribers lines. In brief, this repeater comprises the usual transformer as indicated in the drawing and an alternating current relay RIZ!) connected and arranged to operate only in response to the operation of any one of the magneto generators respectively located at the substations associated with the line 86. This repeater further comprises a ringing relay RIIU which is operative in response to the seizure of the trunk line 55 to cause coded ringing current to be projected over the line 86; a relay R|3 for busying the subscribers line 86 thereby to prevent this line from being seized by any one of the numerical connector switches when the line is engaged in a reverting call connection; a pulsing relay Rl which is connected and arranged to respond to any one of the impulsing devices provided at the substations associated with the line St; and a slow-acting relay R|40 which functions to control the relay RISO. 'Ihe relay R|3IJ further functions to open a point in the loop circuit extending to the line switch 5U, thereby to prevent this line switch from operating to seize one of the selector switches when the line 86 is occupied with a reverting call.

Since the relay RISE) is arranged to be energized only while one of the magneto generators is being operated, it is evident that suitable provision should be made for holding this relay operated continuously during the interval required for a complete reverting call ringing operation and for the further interval which elapses between the end of the ringing operation and the instant when the calling telephone is connected to the line. It is for this purpose that the timing device zii@ is provided. In brief, this timing device comprises a rotary switch 2 5!) having a home position and operative to a predetermined oif-normal position, an output terminal 2|5, means comprising a start relay R2|0 for initiating the operation of the switch 25E] and for applying a predetermined potential, namely, ground potential, to the terminal 2I5, and means comprising the switch 259 and the relays R220, R25!) and R213!! for maintaining ground potential on the output terminal 2|5 for a predetermined time interval. The rotary switch 25|) is of Vthe well-known minor type and comprises a single set of bank contacts 25|, a wiper 252 associated with the contact set 25|, means comprising Yan operating magnet 253 and a ratchet and pawl mechanism, not shown, for driving the wiper 253 over the contacts of the set 25|, olf-normal springs 255, and means comprising a release magnet 254 for causing the switch to be returned to its normal or home position. The arrangement is such that the switch 256 is returned to its home position and starts a new operating cycle each time the start relay RZIIJ is energized. This relay is connected to be energized in response to the operation of any one of the alternating current relays corresponding toand including the relay RI'Zll. Hence, it will be apparent that a new operating cycle of the timing device is initiated each time one of the alternating current relays is caused to operate.

As indicated above, suitable provisions are made for routing test connections from an exchange attendants telephone to the various rural subscribers lines to determine whether or not the lines are faulty. Such connections are routed by way of the test connector switch 6|) to any desired one of the rural lines. Since the selection of the desired one of these lines may occur when the desired line is busy, it is necessary to arrange the apparatus so that the test connector switch cannot gain access to busy lines. To this end, the relay RIM is provided, which relay is normally deenergized but is arranged to operate, only if the line 8S is idle, in response to the operation of the test connector switch 68, to the particular position corresponding to this line. This relay upon operating functions to busy the line, thereby to prevent its seizure by any other of the connector switches and, further, to disconnect the line from the repeater |50.

The operation of the automatic switching apparatus to extend a connection to one of the multiparty rural subscribers lines from one of the other subscribers lines is, in general, quite similar to the operation of the apparatus to set up a connection between the lines |12 and |13 in the manner pointed out above. More particularly, if a call to the substation A is initiated at the substation B, the automatic switch I0 and the swiches 2D and 4D, or other similar switches, may be caused sequentially to operate to select the called line 85 in response to the dialing of the required three digits. Assuming the line 85 to be idle, when the line selecting operation is completed, ground is applied to CI56 by the connector switch 48, thereby to mark the line 86 as busy and to cause the partial operation of the line switch 50 to clear the trunk line |55 of impedances which might interfere with the transmission of ringing and voice frequency currents. As indicated above, each of the connector switches having access to the line 86 and the other rural lines has associated therewith ringing apparatus for applying coded ringing current to the called or selected line. Hence, the calling party, upon 4dialing the nal or code selecting digit or digits, conditions the selected connector switch 40 to apply to the called line 85 coded ringing voltage of the character identifying the called substation A. When the ringing operation is started, the high potential terminal of the ringing generator is connected to CI58 by the ringing relay during each ringing interval and the grounded terminal of the ringing current source is connected to CI51. The application of ground to CI51 results in the com.- pletion of a circuit for energizing RI Ill, this circuit extending from ground on CI51 by way of RAI5I, RC|52 and the winding of RIIU to battery. The relay RI I0 operates at the beginning of each ringing interval to connect, at RAIIII and RCI I5, the line conductor C88 to the trunk line conductor CI58 and to connect, at RAIIZ, the opposite line conductor C81 to the grounded contact RC|I|, thereby to provide an uninterrupted path for the ringing current. This path extends by way of the conductors of the line 88 and through the various ringing devices connected across the line 86, in parallel. Obviously, at the end of each ringing interval, ground is removed from CI51, causing RI I8 to restore. Thus, RI l is repeatedly energized to cause the coded ringing current to be transmitted out over the called line. Since in the present assumed case the projected current is coded in accordance with the signal corresponding to or identifying the substation A, the signal device 16 in its response to this current indicates that the substation A is being called.

The call is answered in the usual manner by removing the receiver 1i from the hook which forms the actuating element for the hook switch 80, causing the springs of this switch to be moved to their respective off-normal positions. When the springs 8| are moved into engagement, the receiver 14 is connected across the conductors C81 and C88 of the line 85 over a path including the secondary winding 12 of the repeating coil 18. When the springs 83 are closed, the transmitter 13 is connected in a closed circuit comprising the primary winding 1I of the repeating coil 10 and the local battery 15. Thus, the receiver lil is connected to respond to voice frequency currents transmitted from the substatian B, and the transmitter 13 is connected to generate voice irequency currents in response to sound waves impinging on the diaphragm thereof. When the springs 82 are moved into engagement, a simplex circuit is completed for energizing the line relay RI58, this circuit extending from ground at the lower spring of the set 82 by way oi the impulsing springs embodied in the impulsing device 11, the lower winding of the ringer 16, C88, RAE, RAIIII, RCII6, the lower winding of RIZ!) and through the winding of Rl to battery. A parallel branch of this simplex circuit extends by way of the upper winding of the ringer 15, C81, RAIM, RAI I2, RCI I3, the upper winding of RIEQ and through the winding of Rl 55 to battery. Although both of the windings of R120 are energized when the above described circuit is completed the fluxes produced thereby are in opposition and, hence, this relay does not operate. The relay'RI5ll, however, operates to complete, at RAI5I and RCI53, a loop circuit extending back to the operated connector switch 58. pletion of this loop circuit causes the operation of the ring cut-01T relay provided in the connector switch 48, in the usual manner. When the ring cut-01T relay operates, the talking connection between the calling and called substations B and A, respectively, is fully completed. The apparatus remains in this condition until the connection is cleared out.

When a connection is once established in the manner described in the immediately preceding paragraphs, it is fully released only when the calling and called parties restore the respective hook switches provided at the substations A and B to normal. Thus, when the calling party at the substation B hangs up, the connector switch 40, the selector switch 28, and the line switch I8 are sequentially restored, in the order named, and in the manner pointed out above. The repeater is released when the called party at the substation A restores the receiver 15 to its hook to interrupt, at the springs 82, the above-traced operating circuit for RI58, this relay being the only operated relay in the repeater. When the switch 80 is returned to normal, the springs 8l are opened to disconnect the receiver 14 from The comf sol across the conductors of the line 86 and the springs 83 are opened to interrupt the abojyietraced circuit including the'transmitter.

Since the line 86 and theV other similar rural linesare of the party line variety, itis incumbent to the substationA C. Before initiating'the call,`

on the line 86. It willv benoted that, when the" latch '85 is moved to the off-normal position, the 'springs 81 are closed to connect the receiver 14' across the conductors of the line 85. Moreover', with this latch occupying the off-normal position, the movable springs of the 'switch 80 are restrained in normal position so that the springs 82 and 83 remain open-circuited. If the line is idle, the calling party may move the latch 85 to its normal position to close the springs-82 and 03; When this is done, theabove-traced circuit including the transmitter 'I3 is completed, the

receiver I4 is connected across the conductors of the line 86, and the simplex circuit, traced above,

is completed for energizing theline relay R150. The relay R150 now operates to complete, at RAI 5I and RC I 53, the above-mentioned loop circuit for'initiating the operation ofthe line switch 50 to select an idle selector switch; "Specifically, this loop circuit extends from the trunk line conductcr C151 by way of RAISI, RC153, RA132, the

repeater winding l163, the resistor 165, the repeater winding' 154`and RA135 to theopposite trunk line conductor C158'. Assuming, for exam-` digit at the substation A to select the connector switch 30, the operation of each of the'two last-j named switches to perform its line selecting and auxiliaryv lfunctions is Videntical with that set forth above. ,In this connection Vitisnoted that, each time the springs'of the impulsing device 'I'I are opened during the ,dialingoperation the op-V erating circuit for R150 is interrupted causing this relay to restore to openvthe loop circuit as extended to either the selector switch 20 or the connector switch 30. Thus,'impulses are transmitted to each of thesetwo'switches to cause vthe line selecting `operations to be'performed. Obviously, when the dialing operation is completed, R150 is held energized and,'in turn, maintains-the loop circuit extending to the line 'switch 50 closed. Immediately the lien switch 50 operates tey extend the loop circuit-to a selectedselectorswitch ground is applied to C156, `thereby Vto mark the line 86 as busy and to prevent its seizure by another of the connector switches. i

The connection as established to the substation C in the manner just described is only completely released when the hook switch is returned to its normal position. Restoration of the switch 80 to normal causes the operating circuit for R155 to be interrupted atthe switchsprings 82. Ground potential is removed from the control conductor C156 when the operated switch train is released. Thus, the repeater 160 is con!- ditioned for further use and the line 86 is marked as being idle. Y 1

As pointed out in the introductory portion ef the specication, the arrangement of the appara-A tus issuch that none of the regular switching equipment provided in the automatic exchange is taken for use Whena reverting call is initiated at one of the substations connected to one of the rural lines. If, for example, a, call to the substation D is initiated at the substation A, the` calling party first actuates the hook latch tc` its off-normal position to connect the receiver 1.4

between the conductors. of the line 86 in the manner pointed out above. The calling party now listens in to determine Whether the line 86 is busy or idle. If the line is found to be idle, the call-y ing party may initiate the call by actuating the hand magneto i8 to project ringing current over the conductors of the line 86. Before performing the ringing operation, however, the calling party should restore the receiver 'Id to its hook and actuate the latch 85 to its normal position. By turning the hand crank of the magneto 18 to generate ringing current coded in accordance with the call signal designating thesubstation D, the signal device at this substation may be caused audibly to indicate that the substation is being called. Each time the magneto l'I8 is operated, current is supplied to the alternating current relay R to cause its operation. The path of this current extends from one terminal of the generator 'i8 by way of the springs 89, the line conductor C8?, RA104, RA112, RC113, the two windings of R120 in series, RCI16,RA114, RAH15, and C88 to the opposite terminal of the generator 18. In response to its energization over the above-traced circuit, R120 operates to complete, at RAE21, a circuit for energizing R and, at RA122, a circuit extending by way of the start conductor C1170 for energizing the start relay R210 provided in the timing device 250.

The relay R130, upon operating, prepares, at RA130, a holding circuit for itself and opens, at RA132 and RAI35, points in the loop circuit extending to the line switch 50. At RAISI, the relay R13E applies ground to the control conductor C156 of the trunk 155, thereby to mark the line aslbusy in the bank contacts of the connector switches to which it extends and to cause the partial operation of the line switch 50 to disconnect all impedances from across the line conductors of the trunk line. At RA133, the relay R130 prepares a circuit for energizing the sloW-to-release relay R140,

Considering now the operation of the timing device 250, when R210 operates, it prepares, at RA21 I and RC2 l2, a circuit for energizing the release magnet 254, opens, at RA214, a point in the circuit for energizing the operating magnet 253, and completes, at RAZIS, a circuit for energizing R220. The last-mentionedcircuit extends from ground at RA213 by way of RA244 and the upper winding of R220 to battery. rlhe relay R220, upon operating, applies, at RAZZI, ground to the output terminal2 I 5 and completes, at RA222 and RC223, an obvious circuit for energizing the pendulum type relay R230. At RA222 and RC224, the relay R230, upon operating, opens a second point in the circuit, traced hereinafter, for energizing the operating magnet 253.

The relay R230, upon operating, completes, at I RA231, RC233 and RC234, an obvious circuit for energizing the sloW-to-release relay R240. The

relay R240, upon operating, prepares, at RA245,

operating Ycircuit for R220. At RA241 and RC2,

the relay R220 opens a point in an alternative circuit for energizing R220. The relay R220 now restores tc open, at RA222 and RC223, the operating circuit for R230 and further to prepare, at

RA222 and RC224, a point in the circuit for energizing the operating magnet 253. When the weighted armature RA23I is released upon the deenergization of R230, it vibrates, pendulum fashion, alternately to engage its two associated contacts RC232 and RC233.

,. stores to open, at RA206, a point in the circuit for energizing the magnet 253. By proper adjustment of the weighted armature RA23I, the time interval during which R200 is held operated may be fixed at any desired value. Preferably, this interval is made sufficient to insure that the ringing operation at the substation A will be completed before R240 restores. When the ringing operation is concluded RI20 restores to open, at RAI22, the operating circuit for R2I0. The relay R2I0, upon restoring, opens at RA2I3, a point in the above-traced operating circuit for R220 and completes, at RA2I4, the above-mentioned circuit for energizing the operating magnet 253. Specifically, the last-mentioned circuit extends from ground at RA222 by way of RC224, RA245, RA2I2 and the winding of the magnet 253 to battery. Upon being energized over this circuit, the magnet 253 attracts its armature, not shown, preparatory to stepping the wiper 252 one step off normal or into engagement with its associated first contact. The actual wiper stepping operation occurs when the relay R240 subsequently restores to open the operating circuit for the magnet 253. When this occurs, the oft"- 4 normal springs 255 are closed to prepare a point in the circuit for energizing the release magnet 254. At this time, however, R2I0 is restored so that the operating circuit for the release magnet is open at RA2I i. With R240 restored and the switch 250 operated to its rst oir-normal position, the above-noted alternative circuit for energizing R220 is completed, this circuit extending from ground at the rst Contact of the set 25I by way of the wiper 252, RA24I, RC242 and through the lower winding o R220 to battery. The relay R220 now operates to again complete, at RA222 and RC223, the operating circuit for R230, causing the latter relay to attract its weighted armature RA23I to recomplete the operating circuit for R240.

From'this point on, the operation of the apparatus is quite similar to that described above, it being in fact a repetition. Thus, when R240 operates, it opens, at RA244, the alternative operating circuit for R220, causing this relay to restore to timing device 200 continues to operate until the wiper 252 is stepped to its eighth oli-normal posiagressif;

tion. When this ocurs, ground is removed at the v wiper 252 and its associated eighth contact'from the output terminal 2 I5, and a point is opened in the alternative operating circuit for R220. Hence, when R240 restores following the ninth step of the wiper 252, no circuit is available for energizing R220 and the cyclic operation of the apparatus is discontinued. The timing device 200 remains in this condition until R2I0 is again energized in connection with another call.

Since the timing device 200 is commonly associated with all of the rural lines and their terminating repeaters and is provided for the purpose of maintaining each of these repeaters guarded against incoming calls during the use thereof in reverting call connections, it Will be apparent that it is desirable for this apparatus to provide at least a minimum guard interval for each of successively initiated reverting calls on different lines. To this end, the device 200 is arranged to be restarted following the initiation of its operation in response to one reverting call and when a second reverting call on a different rural subscribers line is initiated. In explanation of this mode of operation it will be assumed that, at the time the wiper 252 reaches its seventh offnormal position in connection with the reverting call initiated at the substation A, a second reverting call is initiated on a different rural subscribers line. When the alternating current relay corresponding to RI20 and embodied in the repeater terminating this different subscribers line operates, it functions to apply ground to CITI), thereby to cause the operation of R2I0. When R2I0 operates and with the wiper 252 in its seventh oil-normal position, a circuit is completed for energizing the release magnet 254, this circuit extending from ground at RC2I2 by way of RA2I I, the closed off-normal springs 255 and the winding of the magnet 254 to battery. The release magnet, upon operating, causes the wiper 252 to be returned to its home position in the usual manner. Thus, the timing device 200 is in effect restarted. If this device is allowed fully to complete its operation in connection with a single reverting call, it will not be returned to normal until a second reverting call is initiated, thereby to cause the reoperation of the start relay R2I0.

Continuing now with the operation of the apparatus provided in the repeater for guarding the line 86 against seizure 'by one of the connector switches having access thereto, when ground is applied to the output terminal 2I5 through the operation of R220, a holding circuit for RI30 is completed, this circuit extending from ground on the terminal noted by way of C I 'I I RC I 43, RAI42, RAI 34, and the winding of RI30 to battery. With RI30v operated, ground is maintained on the control conductor CI56 to prevent the repeater or, more particularly, the line 85 from being seized by any one of the connector switches at which the trunk line |55 terminates. Following the ringing operation at the substation A the desired talking connection is completed when the calling and called parties remove their receivers from the respective supporting hooks. Vlhen, for example, the receiver 'I4 is removed from its hook to actuate the hook switch 80 to its ofi-normal position, the above-traced circuit for energizing the line relay RI50 is completed. A similar or parallel circuit for energizing RI50 is completed when the called party answers the call. This relay, upon operating, completes, at RAI 54, a circuit extending by Way of RAI 33 for energizing the sloW-to-release relay RI 40. At RAI 5I and RCI52,

the relay RBII opens a point in the operating' lcircuit for RI IU.

Obviously, the relay RI50 is held operated so long as the receiver I4 is removed from its hook and so long as the receiver at the substation D is not replaced on its hook.

-relays RI'Sil, Rill and RI5U are thus held operated until such time as the connection is cleared out at the two substations A and D.

When the receivers at the respective substations A and D are restored to their respective hooks, the circuit over which the line relay RI50 is held energized is interrupted, causing this relay to restore and open, at RAI54, the holding circuits over which RI3 and RI40 are held energized. The relay RI now restores to open, at RAIM, a further point in its holding circuit and, at RAISS, a further point in the operating circuit for R640. When RIG?) restores, the apparatus is entirely released and is in readiness for further use. It is noted that RMB, due to its slow-torelease characteristic, only restores following the restoration of RI3I). Hence, there is no possibility of RIEIB' being maintained energized even though the timing device 200 is operating at the time the connection is cleared out.

As pointed out in a preceding portion of the specication, there is provided in association with the rural lines a test connector switch Si] which may be used in routing calls from an operators substation in the automatic exchange to the lines for the purpose of testing the lines to locate defective apparatus and defective lines'. The method by which a call is routed from the operators telephone by way of the test connector switch to a desired one of the rural subscribers lines is substantially identical to that described above with reference to the operation of the apparatus to establish a. connection between the substations B and C. The method by which this test connector switch is prevented from seizing a selected rural line which is busy is, however, considerably'different from the method employed for busying the lines in the regular connector switches. More particularly, the relay Rlll is provided for preventing the test connector switch from seizing the line S6 when this line is in a busy condition. Relays corresponding to RIOB are provided in association with each of the other rural subscribers lines. When the line 85 is busy in connection with any one of the three types of calls described previously, ground is prese-nt on the control conductor CI56, this ground being impressed on the conductor noted by RISE when the line is busied during a reverting call, being derived from the line switch when the line is busy in connection with a call to one of the other subscribers lines, and being derived from one of the connector switches, such, for example, as the switch 4U, when the line is busy in connection with a call from one of the other subscribers lines to a substation on the line 86. Ground as impressed on CI is extended by way of RAMI and RCIIIZ to the upper terminal of the winding of RIM. As a result, if the test connector switch. Sil attempts tosecure a connection to the line', this line will test busy by virtue of the presence of ground on the test conductor CIBG, this ground being extended through the winding of RIUEI to the conductor noted. Moreover, no circuit will be completed for energizing RIOB since ground potential is also extended to CIBG when the line 86 is selected by the switch 60. Hence, the established talking connection is not interfered with. If, on the other hand, the line 86 is idle at the time the test connector switch attempts to seize the line, battery potential is present on CI56, which potential is extended by way of the resistor IUS, the winding of RIOB and CIIJB to the test contact of the contact set embodied in the switch which corresponds to the line 86. Since ground is impressed on Cl by the switch 60 when the line 86 is selected, RIIl is caused to operate. This relay, upon operating, applies, at' RAII and RCI03, ground to the control conductor CIBG, thereby to mark theline 86 as busy in the various regular connector switches to which the trunk |55` extends. At RAIM and RAIGE, the relay Ri opens two points in the operating circuit for the alternating current relay Ri, thereby to prevent this relay from being energized when ringing current is thereafter conducted by way of the connector switch 69 to the line 86. During the release of a connection routed b-y way of the test connector switch 60 to the line 86, the relay Rlil is caused to restore when ground is removed from CIB. Otherwise, the release of such a connection is accomplished in substantially the manner outlined above with) reference to the connection established between the substations B and C.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is contemplated to cover in the appended claims all such modifications as fall withinthe true spirit and scope of the invention.

We claim:

l. In a telephone system, an exchange, a nonnurnerical switch and a plurality of numerical switches located in said exchange, a repeater, a trunk line terminating at one of said numerical switches and at said non-numerical switch, said trunk line extending to said repeater, a subscribers line extending to said repeater, a plurality of substations associated with said line, means comprising alternating current' generators individually provided at said substations for signaling between said stations on reverting calls, means responsive to the operation of any one of said generators for opening a point in said trunk line, thereby to prevent said non-numerical switch from being seized, means also responsive t'o the operation of any one of said generators for marking said trunk line as busy, thereby to prevent said subscribers line from being seized by said numerical switch, a relay in said repeater and operative to complete a loop circuit to said non-numerical switch thereby to cause said nonnumerical switch to extend the loop circuit to one of said numerical switches, an operating circuit for said relay, and means individually provided at certain of said substations for completing said operating circuit.

2. In a telephone system, an exchange, a nonnumerical switch anda plurality of numerical switches located in said exchange, a repeater, a trunk line terminating at one of said numerical switches and at said non-numerical switch, said trunk line also terminating at said repeater and comprising a normally .incomplete loop circuit extending to said. non-numerical switch, a subscribers line Aextending to said repeater, a .plurality of Ysubstations 'associated with said Vsubscribers line, a relay operative to .complete said loop circuit, thereby to causev said non-numerical switch to extend said loop circuit to one of said numerical switches, an` operating circuit for said relay, mea-ns individually provided at certain of said substations for completing said operating circuit, means comprising alternating current generators individually provided at said substations for signaling between said substations on reverting calls, means responsive to the operation of any one of said generators for marking said trunk line as busy, thereby to prevent said subscribers line from being seized by said one of said numerical switches, and means also responsive to the operation of any one of said generators for opening a point in said loop circuit, thereby to maintain said loop circuit open independently of said relay.

3. In a telephone system, an exchange, a nonnumerical switch and a plurality of numerical switches located in said exchange, a repeater, a trunkl line terminating at one of said numerical switches and at said non-numerical switch, said trunk line also terminating at said repeater and comprising a normally incomplete loop circuit extending to said non-numerical switch, a subscribers line extending to said repeater, a plurality of substations associated with said subscribers line, an impulsing device at one of said substations, a pulsing relay operative to complete said loop circuit, thereby to cause said nonnumerical switch to condition one of said numerical switches to respond to the operation of said pulsing relay, an operating circuit for said relay, said operating circuit being arranged to be controlled by said impulsing device, means at said one substation for completing said operating circuit, means comprising alternating current generators individually provided at said substations for signaling between said substations on reverting calls, means responsive to the operation of any one of said generators for marking said trunk line as busy, thereby to prevent said subscribers line from being seized by one of said numerical switches, and means also responsive to the operation of any one of said generators for opening a point in said loop circuit, thereby to maintain said loop circuit open independently oi said relay.

4. In a telephone system, an exchange, a nonnumerical switch and a plurality of numerical switches located in said exchange, a repeater, a trunk line terminating at one of said numerical switches and at said non-numerical switch, said trunk line also terminating at said repeater and comprising a normally incomplete loop circuit extending to said non-numerical switch, a subscribers line .extending to said repeater, a plurality of substations associated with said subscribers line, an impulsing device provided at one of said substations, a pulsing relay operative to complete said loop circuit, thereby to cause said non-numerical switch to condition one of said numerical switches to respond to the operation of said pulsing relay, an operating circuit for said relay, said operating circuit being arranged to be controlled by said impulsing device, means at said one substation for completing said operating circuit, means comprising alternating current generators individually provided at said substations for signaling between said substations on reverting calls, an alternating current relay including a pair of windings connected and arranged to be diierentially energized in response to the completion of said operating circuit, said windings being cumulatively energized to cause the operation of said alternating current relay 5. In a telephone system, an exchange, a nonnumerical switch and a plurality of numerical switches located in said exchange, a repeater, a trunk line terminating at one of said numerical switches and at said non-numerical switch, said trunk line also terminating at said repeater and comprising a normally incomplete loop circuit extending to said non-numerical switch, a subscribers line extending to said repeater, a plurality of substations associated with said subscribers line, a relay operative to complete said loop circuit, thereby to cause said non-numerical switch to extend said loop circuit to one of said numerical switches, an operating circuit for said relay, means individually provided at certain of said substations for completing said operating circuit, means comprising alternating current generators individually provided at said substations for signaling between said substations on reverting calls, an alternating current relay connected and arranged to operate only in response to the operation of any one of said generators, means responsive to the operation of said alternating current relay for marking said trunk line as busy, thereby to prevent said subscribers line from being seized by said one of said numerical switches, and means also responsive to the operation of said alternating current relay for opening a point in said loop circuit, thereby to hold said loop circuit open independently of said rstnamed relay.

6. In a telephone system, an exchange, a nonnumerical switch and a plurality of numerical switches located in said exchange, a repeater, a trunk line terminating at one of said numerical switches and at said non-numerical switch, said trunk line also terminating at said repeater and comprising a normally incomplete loop circuit extending to said non-numerical switch, a subscribers line extending to said repeater, a plurality of substations associated with said subscribers line, a relay operative to complete said loop circuit, thereby to cause said non-numerical switch to extend said loop circuit to one of said numerical switches, an operating circuit for said relay, means individually provided at certain of said substations for completing said operating circuit, means comprising alternating current generators individually provided at said substations for signaling between said substations on reverting calls, an alternating current relay connected and arranged to operate only in response to the operation of any one of said generators, a relay operative to mark said trunk line as busy, thereby to prevent said subscribers line from being seized by one of said numerical switches, said last-named relay also being operative to open a point in said loop circuit, an operating circuit for said lastnamed relay, said last-named operating circuit being arranged to be completed each time said alternating current relay operates, a holding circuit ior said last-named relay, and means operative in response to the operation of said alternating current relay for completing said holding circuit.

7. Ina telephone system, an exchange, a nonvnumerical switch and a plurality of numerical tending to said non-numerical switch, a subscribers line extending to said repeater, a plurality of substations associated with said subscribers line, a relay operative to complete said loop circuit, thereby to cause said non-numerical switch to extend said loop circuit to one of said numerical switches, an operating circuit for said relay, means individually provided at certain of said substations for completing said operating circuit, means comprising alternating current generators individually provided at said substations for signaling between said substations on reverting calls, an alternating current relay connected and arranged to operate only in response to the operation of any one of'said generators, a relay operative to mark said trunk line as busy, thereby to prevent said subscribers line from being seized by one of said numerical switches, said last-named relay also being operative to open a point in said loop circuit, an operating circuit rfor said last-named relay, said last-named operating circuit being arranged to be completed each time said alternating current relay operates, a holding circuit for said last-named relay, a timying device operative in response to the operation of said alternating current relay for completing said holding circuit and for maintaining said holding circuit completed for a predetermined time interval, and means for maintaining said holding circuit completed independently of said timing device.

8. In a telephone system, an exchange, a nonnumerical switch and a plurality of numerical switches located in said exchange, a repeater, a trunk line terminating at one of said numerical switches and at said non-numerical switch, said trunk line alsso terminating at said repeater and comprising a normally incomplete loop! circuit extending to said non-numerical switch, a subscribers line extending to said repeater, a plurality of substations associated with said Vsubscribers line, an impulsing device provided at one of said substations, a pulsing relay operative to complete said loop circuit, thereby to cause said non-numerical switch to condition one of said numerical switches to respond to the operation of said pulsing relay, an operating circuit for said relay, said operating circuit being arranged to be controlled by said impulsng device, means at said one substation for completing said operating circuit, means comprising alternating current generators individually provided at said substations for signaling between said substations on reverting calls, an alternating current relay connected and arranged to operate only in response to the operation of any one of said generators, a relay operative to mark said trunk line as busy, thereby to prevent said subscribers line from being seized by one of said .numerical switches, said lastnamed relay also being operative to open a point in said loop circuit, an operating circuit for said last-named relay, said last-named operating circuit being arranged to be completed each time said alternating current relay operates, a holding circuit for said last-named relay, a timing device operative in response to the operation of said alternating current relay for completing said holding circuit and for, maintaining said holding circuit completed for a predetermined time intervaly and means for maintaining said holding circuit completed independently of said timing device.

9. In a telephone system, a subscribers line, a

connector switch having access to said line, a plu- ,g

rality of substations associated with said line and individually including telephones, means comprising alternating current generators individually provided at said substations for signaling between said substations, means operative in response to the operation of any one of said generatcrs for marking said' line as busy, thereby to prevent said line from being seized by said connector switch, a timing device for maintaining said lastnamed means operated independently of said generators, means responsive to the operation of any one of said generators for initiating the operation ci said timing device, and means operative in response to the connection of any one of said telephones to said line for maintaining said second-named means operated independently of said timingv device, said last-named means only being operative following the operation of 'one of said generators.

10. In a telephone system, a subscribers line,

va connector switch having access to said line, a

plurality of substations associated with said line and individually including a telephones, means comprising alternating'current generators individually provided at said substations for signaling between said substations, a relay operative to mark said line as busy, thereby to prevent said line from being seized by said connector switch, an operating circuit for said relay, a holding circuit for said relay, means operative in response to the operation of any one of said generators for completing said operating circuit, a timing device for completing said holding circuit and for maintaining said holding circuit completed for a predetermined time interval only, means responsive to the operation of any one of said generators for initiating the operation of said timing device, and means operative in response to the connection of any one of said telephones to said line for maintaining said holding circuit completed independently of said timing device, said last-named means only being operative to maintain said holding circuit completed if said relay is operated at the time said one telephone is connected to said line.

V11. I n a telephone system, a subscribers line, a connector switch having access to said line, a plurality of substations associated with said line and individually including telephones, means comprising alternating current generators individually provided at said substations for signaling between said substations, a relay operative to mark said line as busy, thereby to prevent said lin-e from being seized by said connector switch, an operating circuit for said relay, a holding circuit for said relay, said holding circuit including two branches, means operative in response tol the operation of any one of said generators for completing said operating circuit, a timing device for completing one branch of said holding circuit and for maintainng said holding circuit completed for a predetermined time interval only, means responsive to the operation of any one of said gen,- erators for initiating the operation of said timing device, a second relay operative to complete the other branch of said holding circuit, an operating circuit for said second relay, said last-named operating circuit being pr-epared upon the operation of said first-named relay, and a third relay operative in response to the connection of any one of said telephones to said line for completing said last-named operating circuit and for preparing said other branch of said holding cir-- cuit.

12. In a telephone system, a plurality of subscribers lines, an automatic switch having acc-ess to said lines, a plurality of substations associated with each of said lines, magneto generators individually provided at said substations, a cyclically operating timing device, means individually associated with said lines and each including said timing device for marking the individual ones of said lines as busy, thereby to prevent said lines from being seized by said automatic switch, and control means for said timing device, said timing device and the control means therefor being so connected and arranged that said timing device is started in operation in response to the operation of any one of said generators and the operating cycle thereof is interrupted and a new cycle started in response to the operation of a second of said generators and in the event the rst operating cycle is not completed before the operation of said second generator is started.

13. In a telephone system, a plurality of subscribers lines, an automatic switch having access to said lines, a plurality of substations associated with each of said lines, magneto generators individually provided at said substations, a timing device including a stepping switch having a home position, a start relay operative to initiate the operation of said timing device, said timing device being operative through a predetermined cycle each time the operation thereof is initiated with said switch in said home position, means individually associated with said lines and each including said timing device for marking the individual ones of said lines as busy, thereby to prevent said lines from being seized by said automatic switch, means responsive to the successive operation of said generators or to the repeated operation of one of said generators for repeatedly energizing said start relay, and means for returning said switch to its home position each time said start relay is energized after said timing device has started an operating cycle.

14. In a telephone system, a plurality of subscribers lines, an automatic switch having access to said lines, a plurality of substations associated with each of said lines, magneto generators individually provided at said substations, a timing device commonly associated with said lines and operative through a predetermined cycle each time its operation is initiated, means responsive to the operation of a generator provided at a substation associated with one of said lines for initiating the operation of said timing device, means including said timing device for marking said one line as busy, thereby to prevent said one line from being seized by said automatic switch, means responsive to the operation of a generator provided at a station associated with a second of said lines forY starting said timing device on a new cycle of operation, and means includingV said timing device for marking said second line as busy, thereby to prevent said second line from being seized by said connector switch.

15. Timing apparatus comprising, in combination, a switch having a home position and operative to a predetermined oit-normal position, an output terminal, a start relay, means responsive to the operation of said start relay for initiating the operation of said switch, means controlled by said start relay for applying a predetermined potential to said output terminal, means controlled by said switch for maintaining said predetermined potential on said output terminal independently of said start relay, and means responsive to the operation of said switch to said predetermined oiT-normal position for removing said predetermined potential from said output terminal.

i6. Timing apparatus comprising, in combination, a switch having a home position and operative to a predetermined off-normal position, an output terminal, a start relay, means responsive to the operation of said start relay for initiating the operation of said switch, means controlled by said start relay for applying a predetermined potential to said output terminal, means controlled by said switch for maintaining said pre-- determined potential on said output terminal ndependently of said start relay, and means responsive to a second operation of said start relay for returning said switch to said normal position.

17. Timing apparatus comprising, in combination, a switch having a home position and operative to a predetermined off-normal position, an output terminal, a start relay, means responsive to the operation of said start relay for initiating the operation of said switch, means controlled by said start relay for applying a predetermined potential to said output terminal, means controlled by said switch for maintaining said predetermined potential on said output terminal independently of said start relay, means responsive to a second operation oi said start relay for returning said switch to said normal position, and means responsive to the operation of said switch to said predetermined off-normal position for removing said predetermined potential from said output terminal and for arresting the operation of said switch.

18. In a telephone system, a line, a pair of automatic switches each operative to extend a telephone connection to said line, said line normally being connected to be accessible only to l one of said switches, a relay arranged to be controlled by the other of said switches, said relay being operative to rearrange the connections so that said line is accessible to said other switch, and means operativel when said line is made busy in a connection not routed by way oi said other switch for rendering said other switch ineiective `to control said relay.

19. In a telephone system, a line, a pair of automatic switches each operative to extend a telephone connection to said line, each of said switches having a predetermined operating position corresponding to said line, said line normally being connected to be accessible only to one of said switches, a relay connected and arranged normally to operate in response to the operation of the other of said switches to its said predetermined operating position, said relay being operative to rearrange the circuit connections so that said line is accessible to said other switch, and means operative when said line is tin-ade busy in a connection not routed by way of said other switch for rendering said relay inoperative in response to the operation of said other switch to its said predetermined position.

CARL OMAN WRIGHT. EDWARD SIGFORD PETERSON.

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